Isocyanide adducts of tri- and tetravalent uranium metallocenes supported by tetra(isopropyl)cyclopentadienyl ligands

Abstract

Reactions of uranium(iii) metallocenium salt [(CpiPr4)2U][B(C6F5)4] with tert-butyl isocyanide yielded cationic uranium(iv) products, including a rare example of a linear f-block metallocene complex.

How the Ancillary Ligand X Drives the Redox Properties of Biscyclopentadienyl Pentavalent Uranium Cp2U(═N–Ar)X Complexes

“…[26][27][28][29][30][31] Mixed-ligand metallocene complexes of the type (C 5 Me 5 ) 2 U(X)(Y) (X = halogen; Y= triflate, alkyl, phenyl, amide or imide, ketimide, alkoxide/aryloxide, phosphide) have played a crucial role in the development of organometallic actinide chemistry, serving as potent starting materials for the preparation of various functionalized uranium complexes. 7,12,16,[32][33][34][35][36][37][38][39][40][41][42][43] Several research groups were pioneers in the determination of the redox potentials for a wide range of actinide-containing complexes. 3,4,34,35,[44][45][46][47][48][49][50][51] During the last two decades, the Kiplinger's group provided a large number of experimental data (X-ray structures, E 1/2 half-wave redox potentials, spectroscopic and magnetic measurements) for various U IV /U III , U V /U IV and U VI /U V redox couple of those mixed-ligand complexes.…”

“…Mixed-ligand metallocene complexes of the type (C 5 Me 5 ) 2 U­(X)­(Y) (X = halogen; Y = triflate, alkyl, phenyl, amide or imide, ketimide, alkoxide/aryloxide, phosphide) have played a crucial role in the development of organometallic actinide chemistry, serving as potent starting materials for the preparation of various functionalized uranium complexes. ,,,− Several research groups were pioneers in the determination of the redox potentials for a wide range of actinide-containing complexes. ,,,,− …”

The synthesis and versatile reducing power of low-valent uranium complexes

“…5 In non-aqueous media, a wide range of stable uranium(III) and uranium(V) complexes have been isolated, however, ligands are often found to be incompatible with these oxidation states, as both uranium(III) and uranium(V) may lie outside of accessible redox potentials, may directly oxidize or reduce ligands, or may be susceptible to disproportionation; [6][7][8][9][10][11] oxidation of uranium(III) starting materials to uranium(IV) products may therefore occur during a reaction without clear identification of an oxidant. [12][13][14] Recently, the redox chemistry of uranium was extended to the formal uranium(II) state with the isolation of [K(2.2.2cryptand)][C 5H4SiMe3)3U], 15 although this oxidation state still remains quite rare for uranium. Molecular solution-phase or solid-state uranium(I) or uranium(0) species have not been reported, but a computational study suggested that a monovalent uranium complex may be synthetically accessible.…”

Backbonding in Thorium(IV) and Uranium(IV) Diarsenido Complexes with tBuNC and CO

“…[9,[22][23] There are few thorium complexes with alkyl substituted isocyanide ligands for comparison, Table 1, and their CN stretching frequencies range from 2176-2188 cm À 1 , [24][25][26] Therefore, the thorium isocyanide complex is red-shifted 20-30 cm À 1 from previously reported Th IV compounds. The stretching frequency observed in the uranium complex can be compared to the U III complexes, Table 1, (C 5 Me 4 H) 3 U(CNtBu), [9] (1,3-(Me 3 Si) 2 C 5 H 3 ) 3 U(CNtBu), [27] [(C 5 Me 5 ) 2 U-(CNtBu)(μ-CN)] 3 , [28] and (C 5 iPr 4 H) 2 U(CNtBu)(I), [29] which show ν NC of 2127, 2140, 2143, and 2166 cm À 1 , respectively. For a more direct comparison, U IV complexes with tBuNC have [29,29,30,25,31] ν NC range from 2165-2182 cm À 1 , Table 1.…”

“…The stretching frequency observed in the uranium complex can be compared to the U III complexes, Table 1, (C 5 Me 4 H) 3 U(CNtBu), [9] (1,3-(Me 3 Si) 2 C 5 H 3 ) 3 U(CNtBu), [27] [(C 5 Me 5 ) 2 U-(CNtBu)(μ-CN)] 3 , [28] and (C 5 iPr 4 H) 2 U(CNtBu)(I), [29] which show ν NC of 2127, 2140, 2143, and 2166 cm À 1 , respectively. For a more direct comparison, U IV complexes with tBuNC have [29,29,30,25,31] ν NC range from 2165-2182 cm À 1 , Table 1. Thus, the Th IV complex displays a CN stretching frequency lower than known U IV complexes, while those with U IV complex are similar to those seen with U III ions.…”